Self-Powered Photonic Sensor Using Cholesteric Liquid Crystal Elastomer-Based Sandwiched Architecture with Mechanochromism and Triboelectric Response.

Wearable flexible sensors have aroused great interest owing to their widespread use in medical monitoring, wearable sensing, and human-computer interaction. However, conventional flexible sensors have a single signal response and are susceptible to mechanical damage, thus limiting their potential applications. Here, a self-powered flexible sensor using a cholesteric liquid crystal elastomer (CLCE)-based sandwiched architecture with mechanochromism and triboelectric response is developed. The sensor is constructed by laminating poly(dimethylsiloxane) (PDMS) from two sides to the middle CLCE layer, and a thin silver nanowire (AgNWs) is adhesive to the bottom PDMS layer used as a conductor. Specifically, the dynamic covalent bonds endow PDMS and CLCE layers with excellent self-healing performance, and the CLCE layer has a stable mechanochromism characteristic due to the variations of the helical structure upon mechanical forces. The consequent sandwiched-structure sensor has a fast electric response to the applied pressure with a response time of 139 ms and excellent cyclic response stability, which allows for monitoring human motion, as a self-powered wearable sensor. Finally, a self-powered sensing smart ring for medical monitoring of the patients with mobility problems in the hospital is demonstrated through visualization signals of structural color shift in the daytime, the "LED" light powered by finger tapping in the night-time, or the electric signal response in the special demand. This work demonstrates that CLCE-based self-powered sensors have promising applications in flexible wearables, human-computer interactions, and smart healthcare.